The Ancient Greek aphorism "know thyself" or "gnothi seauton" (Greek: γνῶθι σεαυτόν, transliterated: gnōthi seauton; also ... σαυτόν … sauton with the ε contracted), is one of the Delphic maxims and was inscribed in the pronaos (forecourt) of the Temple of Apollo at Delphi according to the Greek writer Pausanias (10.24.1). The phrase was later expounded upon by the philosopher Socrates who taught that:
The maxim, or aphorism, "know thyself" has had a variety of meanings attributed to it in literature.
The aphorism may have come from Luxor in Ancient Egypt. Pre-Socratics like Thales of Miletus and Pythagoras of Samos are thought by some to have had ancient Egyptian influences, according to Greek folklore and later writers including Aristotle. In any case the saying assumes a distinctive meaning and importance in Greek religion and thought. The Greeks attributed much of their wisdom to Egyptian sources. There are two parts of the ancient Luxor Temple, the External Temple, where the beginners were allowed to enter and the Internal Temple where a person was only allowed to enter after proven worthy and ready to acquire more knowledge and insights. One of the proverbs of the External Temple is "The body is the house of God." That is why it is said: "Man, know thyself". In the Internal Temple, one of the many proverbs is "Man, know thyself, and you are going to know the gods". The ancient Greek aphorism which came from the ancient Egyptian proverb has been attributed to at least the following ancient Greek sages:
- Bias of Priene
- Chilon of Sparta
- Cleobulus of Lindus
- Myson of Chenae
- Pittacus of Mytilene
- Pythagoras
- Solon of Athens
- Thales of Miletus
Diogenes Laërtius attributes it to Thales (Lives I.40), but also notes that Antisthenes in his Successions of Philosophers attributes it to Phemonoe, a mythical Greek poet, though admitting that it was appropriated by Chilon. In a discussion of moderation and self-awareness, the Roman poet Juvenal quotes the phrase in Greek and states that the precept descended e caelo (from heaven) (Satires 11.27). The 10th-century Byzantine encyclopedia the Suda recognized Chilon and Thales as the sources of the maxim "Know Thyself."
The authenticity of all such attributions has been doubted; according to one pair of modern scholars, "The actual authorship of the three maxims set up on the Delphian temple may be left uncertain. Most likely they were popular proverbs, which tended later to be attributed to particular sages."
The ancient Greek playwright Aeschylus uses the maxim "know thyself" in his play: Prometheus Bound. The play about a mythological sequence, thereby places the maxim within the context of Greek mythology. In this play, the demi-god Prometheus first rails at the Olympian gods, and against what he believes to be the injustice of his having been bound to a cliffside by Zeus, king of the Olympian gods. The demi-god Oceanus comes to Prometheus to reason with him, and cautions him that he should "know thyself". In this context, Oceanus is telling Prometheus that he should know better than to speak ill of the one who decides his fate and accordingly, perhaps he should better know his place in the "great order of things."
One of Socrates's students, the historian Xenophon, described some of the instances of Socrates's usage of the Delphic maxim 'Know Thyself' in his history titled: Memorabilia. In this writing, Xenophon portrayed his teacher's use of the maxim as an organizing theme for Socrates's lengthy dialogue with Euthydemus.
Plato, another student of Socrates, employs the maxim 'Know Thyself' extensively by having the character of Socrates use it to motivate his dialogues. Benjamin Jowett's index to his translation of the Dialogues of Plato lists six dialogues which discuss or explore the Delphic maxim: 'know thyself.' These dialogues (and the Stephanus numbers indexing the pages where these discussions begin) are Charmides (164D), Protagoras (343B), Phaedrus (229E), Philebus (48C), Laws (II.923A), Alcibiades I (124A, 129A, 132C).
In Plato's Charmides, Critias refers to the maxim consistently with the view expressed in the Suda, with Critias saying, "for they imagined that 'Know Thyself!' was a piece of advice which the god gave and not his salutation of the worshippers at their first coming in." In modern words Critias gives his opinion that 'Know Thyself!' was an admonition to those entering the sacred temple to remember or know their place and Critias says, " 'know thyself!' and 'be temperate!' are the same. Notice that when the words of Critias are written, 'thyself' and 'temperate' are punctuated with exclamation marks in the English translations, as if they were commands. In the balance of the Charmides, Plato has Socrates lead a longer inquiry as to how we may gain knowledge of ourselves.
In Plato's Phaedrus, Socrates uses the maxim 'know thyself' as his explanation to Phaedrus to explain why he has no time for the attempts to rationally explain mythology or other far flung topics. Socrates says, "But I have no leisure for them at all; and the reason, my friend, is this: I am not yet able, as the Delphic inscription has it, to know myself; so it seems to me ridiculous, when I do not yet know that, to investigate irrelevant things."
In Plato's Protagoras, Socrates lauds the authors of pithy and concise sayings delivered precisely at the right moment and says that Lacedaemon, or Sparta, educates its people to that end. Socrates lists the Seven Sages as Thales, Pittacus, Bias, Solon, Cleobulus, Myson, and Chilon, who he says are gifted in that Lacedaemonian art of concise words "twisted together, like a bowstring, where a slight effort gives great force." Socrates says examples of them are, "the far-famed inscriptions, which are in all men's mouths,--'Know thyself,' and 'Nothing too much'.". Having lauded the maxims, Socrates then spends a great deal of time getting to the bottom of what one of them means, the saying of Pittacus, 'Hard is it to be good.' The irony here is that although the sayings of Delphi bear 'great force,' it is not clear how to live life in accordance with their meanings. Although, the concise and broad nature of the sayings suggests the active partaking in the usage and personal discovery of each maxim; as if the intended nature of the saying lay not in the words but the self-reflection and self-referencing of the person thereof.
In Plato's Philebus dialogue, Socrates refers back to the same usage of 'know thyself' from Phaedrus to build an example of the ridiculous for Protarchus. Socrates says, as he did in Phaedrus, that people make themselves appear ridiculous when they are trying to know obscure things before they know themselves. Plato also alluded to the fact that understanding 'thyself,' would have a greater yielded factor of understanding the nature of a human being. Syllogistically, understanding oneself would enable thyself to have an understanding of others as a result.
The Suda, a 10th-century encyclopedia of Greek knowledge, says: "the proverb is applied to those whose boasts exceed what they are", and that "know thyself" is a warning to pay no attention to the opinion of the multitude.
From 1539 onwards the phrase nosce te ipsum and its Latin variants were often used in the anonymous texts written for anatomical fugitive sheets printed in Venice as well as for later anatomical atlases printed throughout Europe. The 1530s fugitive sheets are the first instances in which the phrase was applied to knowledge of the human body attained through dissection.
In 1651 Thomas Hobbes used the term nosce teipsum which he translated as 'read thyself' in his famous work, The Leviathan. He was responding to a popular philosophy at the time that you can learn more by studying others than you can from reading books. He asserts that one learns more by studying oneself: particularly the feelings that influence our thoughts and motivate our actions. As Hobbes states, "but to teach us that for the similitude of the thoughts and passions of one man, to the thoughts and passions of another, whosoever looketh into himself and considereth what he doth when he does think, opine, reason, hope, fear, etc., and upon what grounds; he shall thereby read and know what are the thoughts and passions of all other men upon the like occasions."
In 1750 Benjamin Franklin, in his Poor Richard's Almanack, observed the great difficulty of knowing one's self, with: "There are three Things extremely hard, Steel, a Diamond, and to know one's self." 
In 1831, Ralph Waldo Emerson wrote a poem entitled "Γνώθι Σεαυτόν", or Gnothi Seauton ('Know Thyself'), on the theme of 'God in thee.' The poem was an anthem to Emerson's belief that to 'know thyself' meant knowing the God which Emerson felt existed within each person.
In 1832 Samuel T. Coleridge wrote a poem entitled "Self Knowledge" in which the text centers on the Delphic maxim 'Know Thyself' beginning, 'Gnôthi seauton!--and is this the prime And heaven-sprung adage of the olden time!--' and ending with 'Ignore thyself, and strive to know thy God!' Coleridge's text references JUVENAL, xi. 27.
In 1902 Hugo von Hofmannsthal has his 16th-century alter ego in his letter to Francis Bacon mention a book he intended to call Nosce te ipsum.
In 1904 Sarah Ida Shaw and Elanor Dorcas Pond founded the Delta Delta Delta fraternity. Part of their motto is Self-Knowledge, Self-Reverence, and Self-Discipline.
The Wachowskis used one of the Latin versions (temet nosce) of this aphorism as inscription over the Oracle's door in their movies The Matrix (1999) and The Matrix Revolutions (2003). The transgender character Nomi in the Netflix show Sense8, directed by The Wachowskis, has a tattoo on her arm with the Greek version of this phrase.
- Pausanias, Description of Greece, Paus. 10.24.
- "Nosce te ipsum - Definition and More from the Free Merriam-Webster Dictionary". Merriam-webster.com. 2010-08-13. Retrieved 16 March 2011.
- "AllExperts.com: temet nosce". allexperts.com. Retrieved 17 February 2013.
- De Lubicz, Isha Schwaller; Lamy, Lucie (1954). Her-Bak: The Living Face of Ancient Egypt. Hodder and Staughton.
- De Lubicz, Isha Schwaller; Lamy, Lucie (1978). Her-Bak: Egyptian Initiate. Inner Traditions International.
- Bias of Priene, in Plato's Protagoras (343a-343b) Socrates lists Bias as one of the seven sources of the Delphic maxims including "Know Thyself." <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343a>
- Chilon of Sparta, a 10th-century Byzantine scholia in the Suda attributed the aphorism to Chilon. "Know Thyself." Suda On Line. Tr. Catherine Roth. 13 Aug 2002. 15 Feb 2011 <http://www.stoa.org/sol-entries/gamma/333>.
- Cleobulus of Lindus, in Plato's Protagoras (343a-343b) Socrates lists Cleobulus as one of the seven sages who were sources of the Delphic maxims including "Know Thyself." <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343a>.
- Doctoral thesis, "Know Thyself in Greek and Latin Literature," Eliza G. Wilkens, U. Chi, 1917, p. 12 (online).
- Myson of Chenae, in Plato's Protagoras (343a-343b) Socrates lists Myson as one of the seven sages who were sources of the Delphic maxims including "Know Thyself." <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343a>.
- Pausanias 10.24.1 mentions a controversy over whether Periander should be listed as the seventh sage instead of Myson. But Socrates who is cited by Pausanias as his source supports Myson. Paus. 10.24
- Pittacus of Mitylene, in Plato's Protagoras (343a-343b) Socrates lists Pittacus as one of the seven sages who were sources of the Delphic maxims including "Know Thyself." <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343a>.
- Socrates, Socrates refers to it in Plato's Philebus 48c, and Phaedrus 229e as a saying of Delphi. The Tufts Perseus web site shows Philebus text as: <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0174:text=Phileb.:section=48c&highlight=thyself,know>.
- Solon of Athens, in Plato's Protagoras (343a-343b) Socrates lists Solon as one of the seven sages who were sources of the Delphic maxims including "Know Thyself." <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343a>.
- Thales of Miletus, a 10th-century Byzantine scholia in the Suda attributed the aphorism to Thales. "Thales." Suda On Line. Tr. Ross Scaife, 28 Nov 2001. 15 Feb 2011. <http://www.stoa.org/sol-entries/theta/17>.
- H. Parke and D. Wormell, The Delphic Oracle, (Basil Blackwell, 1956), vol. 1, p. 389.
- Dempsey, T., Delphic Oracle: Its Early History, Influence & Fall, Oxford : B.H. Blackwell, 1918. With a prefatory note by R.S. Conway. Cf. pp.141-142 (Alternative source for book at Internet Archive in various formats)
- Aeschylus, Prometheys Bound, v. 309: γίγνωσκε σαυτὸν.
- Xenophon describes Socrates use of 'Know Thyself' in Memorabilia 4.2.24 <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0208:book%3D4:chapter%3D2:section%3D24>
- Plato, The Dialogues of Plato translated into English with Analyses and Introductions by Benjamin Jowett, M.A. in Five Volumes. 3rd edition revised and corrected (Oxford University Press, 1892), (See Index: Knowledge; 'know thyself' at Delphi).
- Critias states the meaning of 'know thyself' in Plato's Charmides (165a),<http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0176:text%3DCharm.:section%3D165a>
- Critias says 'know thyself!' and 'be temperate!' are the same in Plato's Charmides (164e), <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0176:text%3DCharm.:section%3D164e>
- Socrates uses the saying 'know thyself' to explain what is important for him to know. http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0174:text%3DPhaedrus:section%3D229e
- Socrates lists the authors of Delphi's sayings. <http://www.perseus.tufts.edu/hopper/text?doc=Plat.+Prot.+343a&fromdoc=Perseus:text:1999.01.0178>
- Socrates seeks to understand 'Know thyself' as pithy, concise wisdom. <http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0178:text%3DProt.:section%3D343b>
- Socrates use of 'Know thyself' in Philebus (48c) http://www.perseus.tufts.edu/hopper/text?doc=Plat.+Phileb.+48c&fromdoc=Perseus:text:1999.01.0174
- 'Know Thyself' as an admonition, in "Know Thyself". Suda On Line. Tr. Catherine Roth. 13 Aug 2002. 15 Feb 2011 <http://www.stoa.org/sol-entries/gamma/333>.
- 'Know the value of Thyself' rightly, in "Know Thyself". Suda On Line. Tr. Catherine Roth. 13 Aug 2002. 15 Feb 2011 <http://www.stoa.org/sol-entries/gamma/334>.
- William Schupbach, The Paradox of Rembrandt's "Anatomy of Dr. Tulp (Wellcome Institute for the History of Medicine: London, 1982), pp. 67-68
- Hobbes, Thomas. "The Leviathan". Civil peace and social unity through perfect government. Oregon State University: Phl 302, Great Voyages: the History of Western Philosophy from 1492-1776, Winter 1997. Archived from the original on 27 November 2010. Retrieved 6 January 2011.
- Alexander Pope begins his Essay on Man Epistle II "Know then thyself."<http://www.harpers.org/archive/2008/03/hbc-90002748>.
- Ben Franklin observes that it is extremely hard to know oneself. <https://books.google.com/books?id=MYkTAQAAMAAJ&dq=Autobiography%2C%20Sayings%20of%20Poor%20Richard%2C%20Letters&pg=PA195#v=onepage&q&f=false>.
- Ralph Waldo Emerson Gnothe Seauton, Poem 1831. <http://www.vcu.edu/engweb/transcendentalism/authors/emerson/poems/gnothi.html>.
- Samuel T. Coleridge wrote the poem 'Self Knowledge' discussing 'Gnôthi seauton' or know thyself. <http://www.readbookonline.net/readOnLine/37203/>.
- McGrath, Patrick (10 January 2011). ""Know Thyself". The most important art lesson of all". patrickmcgrath. Retrieved 3 October 2013.
- "Thompson Surname, Family Crest & Coats of Arms". House of Names. Retrieved 19 April 2017.